package com.ktgj.hotel.utils;

/**
 * 银行卡校验工具类
 * */
public class CheckBankCard {

    /**
     * 校验银行卡号格式
     * */
    public boolean checkBankCard(String bankCard){
        if (bankCard.length() < 15 || bankCard.length() > 19){
            return false;
        }
        char bit = getBankCardCherCode(bankCard.substring(0, bankCard.length() - 1));
        if (bit == 'N'){
            return false;
        }
        return bankCard.charAt(bankCard.length() - 1) == bit;

    }

    /**
     * 从不含校验位的银行卡卡号采用 Luhm 校验算法获得校验位
     * */
    public char getBankCardCherCode(String nonCheckCodeBankCard){
        if (nonCheckCodeBankCard == null || nonCheckCodeBankCard.trim().length() == 0
                || !nonCheckCodeBankCard.matches("\\d+")){
            //如果传的不是数据返回N
            return 'N';
        }
        char[] chs = nonCheckCodeBankCard.trim().toCharArray();
        int luhmSum = 0;
        for (int i = chs.length - 1, j = 0; i>=0;i--, j++){
            int k = chs[i]-'0';
            if (j % 2 == 0){
                k *= 2;
                k = k / 10 + k % 10;
            }
            luhmSum += k;
        }
        return (luhmSum % 10 == 0) ? '0' : (char)((10 - luhmSum % 10) + '0');
    }
}
